This grant application seeks financial support for participation at the University of Vermont in the breast cancer adjuvant therapy protocols of the National Surgical Adjuvant Project for Breast and Bowel Cancers (NSABP). We currently follow 109 patients who have been treated on NSABP protocols 4, 5, 6, 7, 8, 9 and 10, since 1972. We anticipate continued entry of approximately 25 patients per year. The NSABP project headquarters' proposal should be sought for details of protocol rationale and overall scientific achievements of the NSABP. The availability of this patient population at our Clinical Research Center has made and will continue to make possible longitudinal studies on the mutagenic effects of adjuvant chemotherapy and chemoimmunotherapy using the recently developed Albertini/Strauss technique of assaying 6-thioguanine resistant peripheral blood lymphocytes. Additional collaborative studies planned at this institution utilizing NSABP patients will include psychological assessments to monitor the effect of group counseling programs for these patients.